paint
HI bat21
Looking at the photo gallery on this site it would seem that grey is the preferred colour. However I am no expert and all the shades you mention could be correct. if you look in the research and plans section on this site there is a picture (B&W) of the original showing the deck the same as the cabin side.
Unless you intend to build an exact scale model the grey you choose should be OK. Providing you are happy with the finish and it looks good and goes well on the water you will have a most enjoyable model to sail.
Why not start a boat building blog on the site and let us all share your experience as a newbie.
Good luck
Dave
Live long and prosper
Dave